Monthly number of airline tickets sold by a travel agency

he file P14_01.xlsx contains the monthly number of airline tickets sold by a travel agency.

a. Does a linear trend appear to fit these data well? If so, estimate and interpret the linear trend model for this time series. Also, interpret the R2 and se values.

b. Provide an indication of the typical forecast error generated by the estimated model in part a.

c. Is there evidence of some seasonal pattern in these sales data? If so, characterize the seasonal pattern.